Periodic harmonic modulation of a sound source



Feb. 20, 1968 v P. A. BRICOUT 3,369,519,

PERIODIC HARMONIC MODULATION OF SOUND SOURCE Filed Dec. 16, 1964- 2 1 4 Fig.1

H 34 38 M E/vrm 33 3,369,519 Patented Feb. 20, 1968 the 3,369,519 PERIODIC HARMONIC MODULATION OF A SOUND SOURCE Pierre A. Bricout, 10000 Woodhill Road, Bethesda, Md. 20034 Filed Dec. 16, 1964, Ser. No. 418,725 3 Claims. (Cl. 116-27) ABSTRACT OF THE DISCLOSURE A device for generating underwater sonic signals of short duration and high intensity by directing a highvelocity flow of water, subject to Water-hammer effect, into a constantly rotating siren device, the water flow being interrupted by a cyclically operated discharge valve.

The present invention relates to new and useful improvements in signaling devices and more particularly and specifically to improvements in the periodic hydraulic modulation of a sound source.

It is a primary object of the present invention to provide a device capable of generating powerful underwater signals of controlled frequency and in periodic pulses of brief duration, which are capable of long range transmission and the character and identity of which are determinable by conventional sonic receiving apparatus.

Another and important object of the present invention resides in the provision of a rotary siren device to which k powerful bursts of pressure can be applied by suddenly closing a valve at the end of a water conduit into which a high speed flow of water is fed by a pump and to which the continuously rotating siren is permanently connected.

Still another object of the present invention lies in the conversion of the kinetic energy of the water in the conduit into acoustic energy and the generation of a sound pulse when the water-hammer efiect produced by the sudden closing of the conduit applies a burst of pressure to the siren.

A still further object and advantage of the instant invention is a large saving in the mechanical power required for operating the device since the energy storage in the conduit supplies the high instantaneous power radiated during the pulse emission. The pump supplies the much smaller average power absorbed by the device and its size can be reduced accordingly.

Another object of the present invention is the use of a curvilinear reflector or horn for matching the characteristic impedance of the medium propagating the signals to the sonic impedance of the source in view of improving the efiiciency of the latter.

A further object of the instant invention is the use of a diaphragm pressure regulator connected in shunt to the conduit in the immediate vicinity of the siren and of the conduit discharge valve for modifying the length or the shape of the sound pulses emitted by the siren.

Still other objects and advantages of the present invention will become more readily apparent to one skilled in the art when the following description is read in the light of the accompanying drawings.

In the accompanying drawings:

FIG. 1 is a diagrammatic view of the device for periodic hydraulic modulation of a sound source showing the connections of all elements of the system when the source is an underwater rotating siren;

FIG. 2 is a longitudinal section through the rotating siren component of the assembly; and

FIG. 3 is a longitudinal section of the electrically controlled discharge valve at the end of the conduit.

As schematically illustrated in FIG. 1 of the drawings,

the presentinvention would consist of a pump 1 driven by a motor 2, the said pump taking water through the intake pipe 3 from the medium into which the signals are emitted and forcing the said water with highspeed through the discharge member 4 into a large section first conduit 5 hydraulically connected by the member 6 to the member 4, of a continuously rotating siren 7 driven by a motor 8 fitted with a matching horn 9 and in fluid communication through a second conduit 10 with the first conduit 5, of a discharge valve 11 directly opening in the liquid medium 12 propagating the signals the said valve electrically controlled by the enclosed solenoid 13 and terminating the first conduit 5, and eventually of a pressure regulator 14 consisting of a tank 15 connected through a third conduit 16 to the first conduit 5, the said tank containing a flexible diaphragm 17 loaded by a spring 18 therein dividing the tank into two chambers, the resiliency of the diaphragm and/ or the load on the spring being selectively set to control the movement thereof in response to pressure increase in the first conduit 5.

With more specific reference to the accompanying drawings, the rotating siren element 7, detailed in FIG. 2, consists of an elongated tubular shaft 19. Thrust bearings stands 20 and 21 carrying bearings 22 and 23 are mounted at longitudinally spaced points intermediate the remote ends of the shaft and support the same. The shaft 19, intermediate to the thrust bearings, is provided with a drive, preferably a synchronous electric motor, whose stator 24 and rotor 25 are shown in vertical cross section. Instead of a direct drive, a multiplying or reducing gear can also be used as a mechanical connection between the motor and the shaft 19. One end of the latter is closed at 26 and is provided adjacent to the closed end with a plurality of longitudinal, equally spaced slotted openings 27 opening radially of the shaft and disposed about the circumference thereof.

A cylindrical cup-shaped cap 28 is telescopically positioned over the slotted, closed end of the shaft and may be secured, for example, to the adjacent thrust bearing stand 21 to fix the cup-shaped cap in an enclosing position about the closed end of the tubular shaft. The cupshaped cap is provided with radially opening slots 29 formed therein corresponding to the slotted openings in the shaft enclosed therewithin and registering therewith intermittently as the shaft is rotated with the cap member.

The matching horn 9 is a curvilinear reflector secured about the cap member 28, which operates as a sonic impedance transformer, avoids the reflection of the sound emitted by the siren on the liquid medium 12 and thereby increases the sound source efliciency.

That end of the tubular shaft remote to the closed end thereof opens axially into the second conduit 10 which may be, for example, secured to the thrust bearing stand 20 and which is in turn fixed in open communication with the first conduit 5.

The design must be made in such way that the average cross section of the siren is much smaller than the cross sections of the first conduit and of the discharge valve. When the latter is suddenly closed, the water-hammer effect generates a pressure burst proportional to the square of the ratio of the sections offered as a passage to water before and after the closure of the discharge valve.

The shape and/ or the drive of the siren as explained above are given as an example of design and are not limit-ative of the encompassment of the invention. Any source emitting a sonic pulse under a pressure burst can also be used for the same purpose.

The discharge valve 11, as it is best seen in FIG. 3 of the drawings, consists of a piston-type valve body 30 telescopically, slidably positioned in the lowermost open end of the first conduit 5 to move inwardly and outwardly therefrom away from an annular seat 31 fixed in the first conduit annularly within the open end thereof. The valve body carries an extending depending rod 32 which supports at its extended end a magnetic disc 33 which is slidably positioned in a sealed chamber 37 spaced from and aligned with the lower open end of the first conduit 5 and supported by an open cage or spider frame 34.

A solenoid is fixed in the sealed chamber 37 in operable relationship with disc 33 on valve stem 32 in such a manner that excitation of the solenoid will move and retain the disc in a valve opening position against the normal flow in first conduit 5. When the solenoid 35 is de-energized, which is an instantaneous occurrence, the discharge flow in first conduit 5 acting on the surface of valve body 30 Will immediately move it to a seating, closed position.

The solenoid assembly is wired to a control panel 36 at a remote station above the water surface which enables through conventional components as, for example, the synchronous motor operated #403 timer of Industrial Timer Corporation, the timed energization and de-energization of the solenoid assembly automatically upon a selected cycle, to produce timed opening and closing of the discharge valve in the lower end of first conduit 5. The electrical connection is shown schematically by line 38.

The expansion chamber or pressure regulator 14 is in open communication through a third conduit 16 with the first conduit 5 substantially opposite the second conduit 10.

Upon closing of the discharge valve and the attendant rapid pressure build-up, the pressure regulator will absorb a portion of the pressure increase in the first conduit simultaneously with a dissipation of a portion of that pressure increase through the siren. As the siren dissipates a portion of the pressure increase, the expansion chamber or pressure regulator under the influence of its pre-set resilient partition will return the absorbed portion of the pressure increase to the first conduit and hence into the directly opposite siren input thereby permitting an extension or elongation of the pulse signal produced by the siren.

The utilization of a pressure regulator such as 14 is not essential to the operation of the hydraulic siren. However, such a regulator enables control of the pulse amplitude and length to special requirements. Otherwise these pulses factors are fixed products of the length and elasticity of the first conduit 5 and of the ratio of discharge valve to siren cross sections.

In operation of the sonic generator described in the foregoing embodiment, the feed pump 1 above the water level is run at a constant speed under the influence of an electric motor 2 to deliver to the first conduit 5 a constant volume of water picked up by the input feed of the pump from the body of water 12. Most of the flow of water in the first conduit 5 discharges outwardly of the discharge valve 11 at the lower end thereof, which is normally open, and bypasses the siren which delivers only a very weak continuous signal, though its rotor 19 is maintained in rotation by the driving motor 24-25.

In accordance with the timed sequence set up automatically in the control panel 36 the solenoid control for the discharge valve will be energized causing the valve body 30 to move into a closing position in the bottom of the first conduit 5 thereby creating a rapid pressure buildup in the latter which will dissipate in a surge or pulse output through the rotating siren device creating a sonic Wave partially directed by the matching horn 9.

From the foregoing description of an operable embodiment of the present invention, it is evident that an efiicient, effective and powerful sonic wave generator may be provided at nominal cost and with simple operational function. The sonic energy delivered during the pulse results from the conversion of the kinetic energy of the liquid flowing in the first conduit. Such energy can be increased at will by using larger or longer conduits.

Having fully described and explained my invention and having disclosed the construction and operation of an embodiment thereof without intention to limit my concepts beyond the requirements of the prior art and the appended claims, what I claim is:

1. A device for the periodic hydraulic modulation of a sound source emitting underwater sonic pulses, the combination of a pump having intake and discharge members taking water from the medium into which the pulses are generated, a first conduit, said first conduit having inlet and outlet ends, said inlet of said conduit being connected to said pump discharge member, an electrically controlled discharge valve having inlet and outlet portions, said outlet end of said conduit in fluid communication with said inlet portion of the said valve, said outlet portion of the discharge valve having a cross-section approximately equal to the cross-section of the first conduit into which the water is forced with high speed by said pump, a siren whose average cross-section is much smaller than the cross-section of said discharge valve, means operatively connected to said siren for imparting continuous rotation of said siren, a second conduit one end of which is in fluid communication with said first conduit upstream of said discharge valve, the other end of said second conduit in fluid communication with said siren, solenoid means operatively connected to said discharge valve, time control means connected to said solenoid means for effecting cyclical operation of said discharge valve whereby said siren emits a sound of high intensity under the pressure burst produced by the sudden closure of the discharge valve.

2. In the device described in claim 1, the use of a matching horn connected to the siren for improving its efficiency.

3. In the device described in claim 1, the use of a diaphragm pressure regulator connected by a third conduit to said first conduit in the vicinity of the siren, the said pressure regulator modifying the length and/ or the shape of the sound pulse emitted by the siren.

References Cited UNITED STATES PATENTS 1,131,764 3/1915 Williams 116-147 1,143,703 6/1915 Hecht l16147 1,162,719 11/1915 Hecht 34012 1,463,507 7/1923 Hahnmann 34012 1,475,385 11/1923 Hecht et 'al 11627 FOREIGN PATENTS 297,978 8/ 1919 Germany.

LOUIS J. CAPOZI, Primary Examiner. 

